HDFC Bank — cash bank not received for purchase of iphone11

Hi all,

I had purchased iphone11 from croma on january-26-2020. As per the offer there was a flat cash back of rs 6000/- also specified in the bill to be credited within 120 day. Now its more than 120 day and i have not received the cash back. On calling hdfc bank i was asked for offer details and was said the marketing team will check and revert before 08-jun-2020.
I feel the bank should now about its offer and not tell customer that it would check and inform. It create a doubt on the customers mind.